Alert archive / New Jersey / Mesoscale Discussions in 2021
Mesoscale Discussion 1673
The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2021, 4:28 PM EDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 1, 2021, 4:28 PM EDT (20:28 UTC)
- Expired
- Sep 1, 2021, 6:30 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 483
Counties New Castle County, DE, Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Hudson County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Ocean County, NJ, Salem County, NJ, Somerset County, NJ, Union County, NJ, Bronx County, NY, Kings County, NY, Nassau County, NY, New York County, NY, Queens County, NY, Richmond County, NY, Delaware County, PA, Philadelphia County, PA
The radar
The Philadelphia radar (KDIX), 27 km from the middle of the area, began a volume at 20:31 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Brookhaven, NY (KOKX), launched 12:00Z, 8.5 hours before the alert went out and 145 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 51 J/kg
- Mixed-layer CIN
- -80 J/kg
- Mixed-layer LCL
- 1274 m above ground
- 0-6 km bulk shear
- 22 kt
- 0-1 km storm-relative helicity
- 31 m²/s²
- 0-3 km storm-relative helicity
- 201 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.2
The text
As transmitted.
782
ACUS11 KWNS 012028
SWOMCD
SPC MCD 012028
NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-012230-
Mesoscale Discussion 1673
NWS Storm Prediction Center Norman OK
0328 PM CDT Wed Sep 01 2021
Areas affected...southeast Pennsylvania...Delaware...New
Jersey...Long Island
Concerning...Tornado Watch 483...
Valid 012028Z - 012230Z
The severe weather threat for Tornado Watch 483 continues.
SUMMARY...Storms are likely to increase in coverage and spread
east/northeast across New Jersey and eventually Long Island.
Damaging gusts and perhaps a tornado will be possible. An additional
watch could be needed later today.
DISCUSSION...A large mass of storms currently exists just north of a
warm front over southeast PA, with an additional cluster moving
northeastward out of MD and northern DE. The warm front currently
extends east across central NJ, and has been moving north at around
8 kt.
The conglomeration of storms over southeast PA will likely spread
east along and north of the warm front, with damaging gusts
possible. Shear will remain favorable for periodic supercells or a
brief tornado near this boundary which is likely to affect Long
Island later this evening.
Storm mode trends currently suggest that wind may become the primary
risk, especially if the storms remain north of the front. However,
any cells that may develop along the front itself could possibly
produce a brief tornado as low-level SRH remains favorable.
..Jewell.. 09/01/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OKX...PHI...LWX...
LAT...LON 39767376 39337553 39467588 39637593 39877575 40027545
40237520 40457495 40727449 41057304 40947278 40717271
40557275 40287287 39767376SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 1, 4:01 AM EDT | Mesoscale Discussion | SPC | New Castle | 119 min |
| Sep 1, 11:03 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 2 hr |
| Sep 1, 12:40 PM EDT | Tornado Watch | SPC | Kent, New Castle, Sussex | 9 hr |
| Sep 1, 3:09 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 3 hr |
| Sep 1, 6:22 PM EDT | Tornado Watch | SPC | Bergen, Essex, Hudson, Passaic, Union | 7 hr |
| Sep 1, 6:34 PM EDT | Mesoscale Discussion | SPC | Burlington, Camden, Gloucester, Hudson, Mercer, Middlesex and 3 more | 56 min |
Nearby
Mesoscale Discussions in New Jersey, 2021Mesoscale Discussions in New York, 2021Mesoscale Discussions in Pennsylvania, 2021Every mesoscale discussion in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.